Actually I would not be so quick to reject your brothers thinking as "delusional." Just explaining my answer is complicated and I feel some of your brothers frustration. We humans have a tendency to blind ourselves to that which we don't understand. We ignore, discount, and explain away evidence of the things we don't understand. Sometimes the delusional thinking is what we use to ignore the reality we don't understand. The reading of the note inside the sealed envelope is called remote viewing. We (US) spent millions researching this phenomenon. The research was supervised by a group of physicists and psychologists. Some of the results are not easily dismissed so we try hard to forget, discount, or explain then away. I believe it can and has been done, but its just not reliably enough to count on.
http://www.scientificexploration.org/jo ... 1_targ.pdf Secondly, you may be misunderstanding some of what he says. Theoretical physicists are already thinking on the math, physics, and engineering necessary to create worm holes which will permit us to transcend space and time, and even creating singularities and entire universes. Perhaps your brother has been reading some of Brian Grene's books. Even more "out there" is some of the work being done by David Duetshe of London.
One the fastest growing religions todays is Mormonism. It is based upon the visions (delusions) of Joseph Smith who is today worship by millions as a prophet.
Sounds like your brother likes sharing his understanding of reality but is frustrated by others dismissing him as delusional. He sounds like a smart kid. Some imaginative type people live rich fantasy filled lives. Nothing wrong with that. In fact the fantasies sometimes lead to great discoveries. Has he been in contact with aliens? Probably not, but I can't reject that. Has he successfully done some remote viewing and transcended space with his mind. I suspect he probably has and you can probably do it too.